Abstract: In order to improve the accuracy of test results, the measurement uncertainty of phenol in mainstream cigarette smoke by high performance liquid chromatography (HPLC) was analyzed and evaluated. The mathematical model for measurement uncertainty assessment was established and the sources of uncertainty were identified. The results indicated that the main sources of uncertainty were smoking process, measurement repeatability and the process of standard solution preparation. The standard uncertainty of measurement results was 0.2μg/cig and the expanded uncertainty was 0.4μg/cig (k=2) at the confidence level of 95%.